1. Field of the Invention
The present invention relates to a vehicle lamp equipped with an LED (light-emitting diode) light source. More particularly, the invention relates to a vehicle lamp geometrically configured such that its reflection surface reflects light in substantially a uniform manner.
2. Description of the Related Art
Many vehicle lamps equipped with an LED light source have recently been adopted. In this regard, German Patent Application Laid-Open No. 19638081 describes a vehicle lamp. The vehicle lamp is constituted such that light originating from an LED light source is converted into collimated light by means of a Fresnel lens such that the collimated light is reflected forward of a lamp by means of a reflector.
In the vehicle lamp described in the German publication, the reflector has a stepwise reflection surface in which there are alternately formed a plurality of light incidence sections where the collimated light exiting from the Fresnel lens enters and a plurality of plane-like intermediate sections where no collimated light enters. When the lamp is observed from the front thereof, the reflection surface of the reflector can be readily seen to be glaring over the entire surface at the reflection surface.
However, an intermediate section of the vehicle lamp described in the patent publication (where the collimated light exiting the Fresnel lens does not enter) becomes a non-illuminating section. Hence, the light incidence sections look glowing, resembling spread spots, but an intermediate section of the light incidence section looks dark. Thus, there arises a problem of a failure to make the reflection surface of the reflector glare in substantially a uniform manner.
The invention has been conceived under the foregoing circumstances and aims at providing a vehicle lamp which is equipped with an LED light source and can make a reflection surface of a reflector glare in substantially a uniform manner.
The invention attempts to achieve the foregoing object by designing the geometry of an intermediate section of a reflection surface.
The invention provides a vehicle lamp having a light source (in the embodiment, a LED light source), an optical member for converting light originating from the LED light source into collimated light, and a reflector portion for reflecting the collimated light exiting from the optical member forward of the lamp, wherein
the reflector portion has a stepwise reflection surface in which there are alternately formed a plurality of light incidence sections into which the collimated light enters and a plurality of intermediate sections into which no collimated light enters; and
at least a portion of the intermediate sections is formed from an irregular surface formed so as to recess rearward of the lamp with respect to a plane parallel to the direction of radiation of the collimated light.
Here, the term xe2x80x9cvehicle lampxe2x80x9d is not limited to a vehicle lamp of specific type. For instance, a tail lamp, a stop lamp, or another lamp can be adopted.
In addition, no particular limitation is imposed on the specific configuration of the xe2x80x9coptical member,xe2x80x9d so long as the optical member can convert the light originating from the LED light source into collimated light. For example, a Fresnel lens, a convex lens, or a concave mirror can be adopted. At that time, the xe2x80x9coptical memberxe2x80x9d may or may not have another cross section for converting the light originating from the LED light source into collimated light, so long as the optical member is configured such that the light originating from the LED light source is converted into collimated light by-means of one cross sectional surface extending in the longitudinal direction of the lamp including the luminescent center of the LED light source.
The term xe2x80x9creflector portionxe2x80x9d may denote an ordinary reflector portion configured to reflect the collimating light exiting from the optical member on an outer surface of the reflector portion. Alternatively, the reflector portion may be formed from a transparent member such that the collimated light exiting from the optical member having passed through the reflector portion is subjected to internal reflection.
In relation to the xe2x80x9creflection surface,xe2x80x9d no particular limitation is imposed on the arrangement of light incidence sections and intermediate sections, so long as a plurality of light incidence sections and a plurality of intermediate sections are formed stepwise and alternately.
No particular limitation is imposed on the specific geometry of the xe2x80x9clight incidence section,xe2x80x9d so long as the light incidence section is formed so as to reflect the collimating light exiting from the optical member forward of the lamp. Further, there may be adopted a light incidence section configured to subject the collimated light exiting from the optical member to mere regular reflection. Alternatively, the light incidence section may be configured to subject the collimated light exiting from the optical member to diffusion and reflection.
The xe2x80x9cirregular surfacexe2x80x9d constituting each intermediate section is not limited to any particular geometry, so long as the irregular surface is formed so as to recess rearward of the lamp with respect to a plane parallel to the direction of radiation of the collimated light exiting from the optical member.
As indicated by the foregoing configurations, the vehicle lamp of the invention is configured to convert the light originating from the LED light source into collimated light by means of an optical member. The collimated light exiting from the optical member is reflected forward of the lamp by means of a reflector. The reflector portion has a stepwise reflection surface in which there are alternately formed a plurality of light incidence sections into which the collimated light enters and a plurality of intermediate sections into which no collimated light enters. At least a portion of the intermediate sections is formed from an irregular surface formed so as to recess rearward of the lamp with respect to a plane parallel to the direction of radiation of the collimated light. Hence, the following working-effect can be obtained.
Specifically, in relation to the vehicle lamp equipped with the LED light source, generally the LED light source is optically designed as a point source of light. In effect, an illumination section of the LED light source has a somewhat light-emitting area, although the area is small. Further, a manufacturing error or a mount error inevitably arises in the optical member or the like. Consequently, the collimated light that originates from the optical member and enters the reflection surface of the reflector portion has some degree of broadness.
If at least a portion of the intermediate sections constituting the reflection surface is formed from an irregular surface, stray light (an oblique ray) included in the collimated light originating from the optical member can be reflected forward of the lamp by means of the irregular surface. As a result, when the lamp is observed from the front, the reflection surface of the reflector portion can be made such that the intermediate section formed from the irregular surface also appears to glow and also as such that the light incidence section appears to glow, resembling spread spots. At that time, the irregular surface constituting the intermediate section is formed so as to recess rearward of the lamp with respect to the plane parallel to the direction of radiation of the collimated light exiting from the optical member. As a result of the intermediate sections being formed from irregular surfaces, incidence of light onto the light incidence sections is not hindered.
According to the embodiment, in the vehicle lamp equipped with the LED light source, an area on the reflection surface of the reflect or portion where the intermediate section is formed from the irregular surface can be made to glare in substantially a uniform manner. At that time, as long as the intermediate section is formed from the irregular surface over the entire reflection surface of the reflector portion, the entire reflection surface of the reflector portion can be made to glare in substantially a uniform manner.
As mentioned previously, the specific geometry of the xe2x80x9cirregular surfacexe2x80x9d is not limited to any specific geometry. If the cross-sectional profile of the irregular surface is set to a saw-toothed profile, the stray light included in the collimated light exiting from the optical member can be reflected forward of the lamp efficiently.
In the configuration, at least a portion of the reflection surface of the reflector portion is formed as an internal reflection section for reflecting the collimated light exiting the optical member forward of the lamp through internal reflection. At least the intermediate section located in the internal reflection section is formed from the irregular surface. As a result, the following working-effect can be yielded.
Specifically, the collimated light entering the internal reflection section travels through the reflector portion. Hence, the stray light included in the collimated light exiting the optical member enters the irregular surface of the intermediate section, and the collimated light exiting the optical member is also subjected to scattering by means of impurities or the like within the reflector portion. Stray light stemming from repeated internal reflection and stray light stemming from a portion of the light subjected to diffusion and reflection forward of the lamp by means of the light incidence section being internally reflected from the front surface of the internal reflection section enter the irregular surfaces of the intermediate section. Consequently, when the intermediate section located in the internal reflection section is formed from the irregular surface, the internal reflection section can appear to glare more brightly. As a result, the internal reflection section can be made to glare in substantially a uniform manner.
When at least a portion of the reflection surface of the reflector portion is formed as an internal reflection section, at least a part of the reflector portion is formed from a translucent member. In such a case, when the optical member is also formed from a translucent member, the translucent members can be formed as a single member.